Constantly
by lembas7
Summary: Mycroft Holmes did not set out to be nothing more than a side character in his brother's story. To his regret, he succeeded at it anyway.
1. Constantly

**Disclaimer:** Transformative work.

 **A/N:** Don't ask me what I'm doing, because I don't know.

 **Summary:** Mycroft Holmes set out to be nothing more than a side character in his brother's story. And he succeeded.

* * *

CONSTANTLY

Mycroft Holmes was unplanned.

He deduces this within moments of discerning Mummy' third pregnancy, though she herself won't have confirmation of that condition for another four days. He works to replace the word _realize_ with _deduce_ in his vocabulary on that same day.

 _Realizations_ , he finds, are more painful than they are worth.

It wasn't very difficult. Seven years between Mycroft and Sherlock, and now, with Sherlock mere months old, another child on the way.

Mummy had never made a secret of wanting children.

But with just the two of them it might have been either whose timing was less than optimal. Granted, Mycroft had taught himself to read by age three; using a combination of public television programming and Mummy's dissertation notes. He was aware, even then, that things other than himself absorbed the majority of his parents' time.

In retrospect, he might have deduced it sooner, but he had lost the first three years of life to the development of necessary gross and fine motor control, as well as language absorption and literacy. For the remaining four years, he feels he has no excuse, small sample size notwithstanding.

It became increasingly obvious when Mummy resigned from her position, giving up a chance at tenure and access to some of the most intelligent minds in her field – to spend her time entirely at Musgrave, with her focus most determinedly on the nursery in a way Mycroft had never seen. Not even when he occupied it.

He had never felt unwanted or unloved by either of his parents. After all, there were ways of taking care of such things before the problem emerged, squalling, into the world, at which point analogous action carried a murder charge. But it becomes apparent he was rather inconvenient, nonetheless.

In a small room, in a corner of his mind where he rarely voluntarily ventures, is a place very much like the space beneath the covers of a bed at night, where the room is brightened only by a slit of light shining under the door from the hallway, itself unlit and only carrying along its length the light of an open door to a master suite situated at the far end. Loud voices, indistinct, arguing – and frequent enough that he has tried not to hear, rather than the converse.

He knows, fully and well, that he would not exist absent an accident, of which type he would prefer not to dwell. He had known it academically before this deduction, but nothing drives a point home like personal experience. That, too, is a lesson.

It is to his advantage to be both unpredictable and underestimated.

Naturally, therefore, he sets about being as overtly predictable as possible. There is some luck in his parents' distraction during his early years; while he had broken many curves before he realized they were there, it's not too late to slot himself firmly into the category of "remarkable," and avoid the type of higher classification that comes with serious attention. In the course of this undertaking, he ends up calculating himself into some rather annoying weight gain; but a visible flaw deters most everyone from probing deeper for weaknesses, and genetic predisposition makes it the most convenient solution.

There are times, with Sherlock, where he feels his loneliness and misgives the entire endeavor as useless.

What possible benefit could accrue to mask himself so thoroughly, he posits.

Intuition – _data processed too fast for the conscious mind to comprehend_ – and his original deduction convince him to continue this exercise as an experiment, at least until his teenage years. He promises himself that, if by the time puberty and its attendant hormones could excuse it, the data weighs sufficiently against continuing in this vein, he might discontinue the guise then and allow biology to take the blame for the differences.

Before he has finished collating the data, Eurus turns five.

Victor Trevor dies.

Musgrave burns.

* * *

It isn't until Mycroft is twelve that his parents have them all "professionally assessed." Less than a day after Eurus is found attempting to skin herself, Mycroft picks up the phone in his parents' room, muffling the receiver, and listens to his father make the appointment in London for one week hence.

He prepares. He reads all the psychology texts immediately to hand, as well as the relevant child-rearing materials Mummy and Father had sought when Sherlock had started to come into his own. He secretes them away where neither Sherlock nor Eurus can get to them. Eurus, at least, is still at the point where she doesn't grasp the need to disguise her actions. Sherlock is incapable of the type of actions that need disguising. But he and Eurus are willing co-conspirators in minor acts of piracy around the house; the thieving of cookies, hiding of treasures, and so on. Sherlock finds Eurus a subpar but acceptable substitute when Victor cannot come out and play. Eurus finds Sherlock a useful tool, as he has thirteen months and a handful of centimeters on her, with a proportionately longer reach.

So Mycroft hides the books.

Perhaps, perhaps there might be useful information gleaned about the status of his sister from this venture.

He is intelligent enough to fear her.

Mummy, Father, and Sherlock don't. He knows it's not a lack of intelligence on their part, or cunning on Eurus's – she doesn't yet see the need for that. Sherlock, at least, lacks the data to provide sufficient context for her actions. They are, all three of them, extraordinary – and that is Sherlock's normal.

The only answer for his parents' blindness, is sentiment.

Mycroft does not claim to be immune to that particular failing, but he loved Sherlock before Eurus existed.

Which is not to say he does not love his sister. But he is fully aware that she is fixated on Sherlock; that age alone makes them closer to one another than either will ever be to him. And that was before Eurus started teaching Sherlock the violin.

It's not that Eurus doesn't care for Mycroft; it's that she cannot care about him.

He fears the very real possibility that she cannot care about anyone.

London is ultimately illuminating, but not as illuminating as he had hoped. His own results are perfectly calculated in accordance with his image, no surprises there. Sherlock is brilliant, and sweet, and loving; also unsurprising. Eurus is incandescent, burning so brightly she scorches all around her with no care if she burns them, or herself, to ash.

Mycroft knows that eventually, she will try. It is only a matter of when.

* * *

He's not there when Victor Trevor dies.

No one knows when it happens exactly, but the boy is not recovered. In the years following, Mycroft calculates the variables, and for each possibility of what Eurus might have done, he has mentally marked a time of death. None exceed a few days. Not for a child of that age.

It's not until the disaster at Sherrinford that he is able to pin a proper range on the matter. Specifics – the temperature in the well that day, the level of the water, the boy's physical condition and any soft-tissue injures – will never be known. Nor will he ever learn how Eurus discovered the well, when no one else knew it was there. She certainly isn't telling.

But at the time, he doesn't hear about it at all until his mother calls _grand-mère_ to have him sent back to Musgrave. He'd been… inconvenient, again, to be sent off in the first place. But Sherlock is in hysterics, begging for Myc, and hearing that turns Mycroft into a tight-taut wire until he gets home. The stress of the journey and the weeks that follow dissolve fifteen pounds from him, not that anyone notices.

By the time he arrives, Eurus refuses to sing in more than broken snatches.

He's not meant to play this game with her. No one thought to write down what she was saying.

A month later, the Trevors bury an empty coffin.

It's too late to save his relationship with Sherlock.

Sherlock, who he loves more than his own life. Sherlock, who had mutely begged his big brother to find his best friend. Sherlock, who had been unable to repeat Eurus's words and, along with everyone else, failed to induce her to repeat herself in full now.

Mcyroft knows he will never stop blaming himself, either.

He knew something was coming, though he never knew precisely what, or when. He had calculated, and deduced; and in an abundance of caution run the variables again, this time with the mathematically sound assumption that Eurus's intelligence exceeded his own.

He doesn't know if it does or not. He doesn't have the rubric to the tests he faked his way through, nor could he get his hands on more than the diagnosis for Eurus. Not at twelve.

What he does know is that, even at thirteen and armed with knowledge, logic, and Eurus's clinical diagnosis, his parents will not listen to him. Will instead decide he needs some time away, to himself. So they can concentrate on said diagnosis, he deduces, and ways to convince themselves it is a mistake.

And of course, that Eurus can recognize opportunity when it presents itself.

He also knows that Eurus is not finished. That she is, to the best of her meagre ability, furious – at Sherlock, at Mycroft, at Mummy and Father.

And Eurus has always been fascinated with fire.

* * *

Mycroft trained himself to sleep lightly when Sherlock was born. Often, during Mummy's pregnancy with Eurus, he would sneak into Sherlock's room and check on him in the night. Sometimes, he could stave off a bout of crying with a bottle or clean nappy, so that Mummy and Father could sleep.

He doesn't lose the habit when Eurus is born, tending more earnestly to his brother while Eurus is in the bassinet in Mummy and Father's room. When he wins the argument to have Sherlock's crib in his room it's less due to the strength of his arguments and more to Father finding him asleep on the carpet in Sherlock's room a time too many.

At night, with Sherlock securely asleep, Mycroft whispers secrets into the head of black curls so dissimilar to his own. During the day he does deductions, reduced to something appropriate for Sherlock's age, and begins teaching him word-picture recognition.

By the time of Victor Trevor's death, they have separate rooms – Mummy and Father's insistence, as Mycroft is growing up. He sees the necessity, of course.

It's still not to his preference.

It's useful, however.

The night of the fire, Eurus doesn't quite have enough time to block his door as she'd blocked Sherlock's, and their parents'. Being an afterthought works to his advantage again. He doesn't know if she ever intended to do so – the smoke wakes him, and he has retrieved Sherlock and is on his way to Eurus's room when Father intercepts him, and takes them both out to the lawn. Mummy is there, with Eurus. His sister was already there, waiting.

She doesn't stop watching, even as the roof collapses.

Sherlock's silence is completely different; the stare of his eyes blank with shock.

Mycroft feels the heat from the house even yards away, but the coldness in Eurus's eyes makes him shiver.

He never knows if Father knew that Eurus blocked their parents' bedroom door. Mycroft didn't know until after; walking the perilous upstairs while one of the village fire brigade made disparaging mutterings under his breath about Mycroft's weight and the integrity of the floor. But the collection of scratches gouged deep into the floorboards where the door would swing, and the melted plastic and metal strewn all around, spoke volumes.

She hadn't bothered with subtlety at Sherlock's room, wedging a chair beneath the door in what would have been an improbable grasp of physics for any other child her age.

Mycroft doesn't say anything when Uncle Rudi takes her away.

* * *

Two years after the fire, Sherlock browbeats four different psychiatrists with his intelligence before learning enough about the field to get the result he wants. One idiot finally renders an official diagnosis, and forever after Sherlock flings it, weaponlike, against anyone who objects to his outrageous behavior. Being a "high-functioning sociopath" is his shield against the world.

He needs one, as his brother is apparently useless at the task.

* * *

 _I'm the smart one._

He may have some intelligence, but Sherlock – a bright, happy, healthy Sherlock – will outstrip him by far in all ways.

He sees it, in the days after Sherrinford.

After telling Mummy and Father, and receiving his censure. Nevermind that the original decision had never been his – at fifteen, he'd had as much success getting an adult to pay serious attention to him as he had at thirteen. Which is to say, none. Uncle Rudi had taken Eurus, manufactured the second fire, and given his parents peace. Mycroft himself had believed it for a time.

By the time he deduced otherwise, years had gone by. An empty coffin, like Victor Trevor's, rotted away beneath a stone carrying Eurus's name. He'd never known if – _how_ – he should tell his parents that it had all been a lie. He'd thought he'd managed to do the right thing, for once.

But he can't let Sherlock – the only innocent in this – bear the responsibility of breaking the news. Instead, he lets Mummy's anger wash over him; Father's pain hit him square on. He bites his tongue on the signs that Eurus had blocked their doors once upon a time, and resigns himself to being…. inconvenient, once again.

The way Sherlock and Eurus play together makes Mummy smile, and Father's shoulders loosen. He never could compare to either of them. He never tried – it was a battle he knew from the outset he would not win, not when he made that first – _only_ – apparent and relevant deduction upon knowledge of Eurus's impending existence.

They play, and play.

He wonders if he's the only one in the room, in those moments, who remembers Victor Trevor. He sees Sherlock's face, once, as he twists in the throes of music, and knows he isn't. It's a sharp reminder – that this is Sherlock's bildungsroman, and Mycroft is a minor character at best.

* * *

Mycroft Holmes has family; but he has no pressure points.

He wonders, sometimes, what he might have achieved beyond his current status, had every move he made not been calculated with his family's protection in mind.

He has no pressure points because his parents are mundane and harmless, closets blessedly free of skeletons. His sister is a buried unknown; to those who know, his cold indifference to her is sufficient to remove her from consideration. His brother is shameless in his faults, the most serious of which would garner Mycroft sympathy rather than censure. In that, his greatest weakness is hidden. It has always been Sherlock.

Sherlock's weakness will never be Mycroft.

Over the years, he has become a third, unnecessary, pseudo-parental figure to Sherlock, and is only resented for it. He knows it – in fact, it is almost impossible not to see the resentment. But he is unable to stop, as the overdoses continue and it is only his intervention that shields his parents from the worst of it; only his resources that help Sherlock get clean (though they cannot keep him that way); only the last of his influence that garners a promise from Sherlock to make a list – a list that has, more than once, saved Sherlock's doctors precious seconds and, accordingly, Sherlock's life.

He is reviled by his only brother, more than once.

He accepts it as his due for past sins, and refuses to dwell.

* * *

 _Moriarty slipped up. He made a mistake. Because the one person he thought didn't matter at all to Sherlock, was the one person that mattered the most._

Mycroft hears those words – legacy of a last tracker sewn into Sherlock's coat. He tastes true bitterness for the first time, in a long time, knowing that for all his aide to his brother, Moriarty would never have bothered to aim a bullet at him. That those words were never – and will never be – meant for him is another blow, squarely in the heart he had armed and armored since Sherlock was born.

Nothing he does will ever make up for failing Victor Trevor, and thus, Sherlock.

He goes home that night, and hides in the room he'd had carefully mismarked on the architectural plans as a walk-in closet to a guest room. It's an indulgence he couldn't bear if anyone knew about, even though it has no particularly distinguishing touches and certainly no information relevant to anyone who was never in the room he inhabited in his babyhood, before Sherlock and Eurus and even before Musgrave. The particular shade of green on the walls matches none of the décor of the rest of the home, but Mycroft has always found it soothing. The furniture is old and battered, but his parents never realized that he managed to recover it from the thrift store they'd left it at when vacating the suburban London home for Musgrave when Mummy was pregnant with Sherlock.

When Sherlock invades his home with a clown and a child and cheap tricks, in a prelude to the disaster at Sherrinford, that room remains thankfully ignored. It is the first place he returns when released after days in the cell at Sherrinford. He thinks about those words. He thinks about the way Sherlock put a gun under his chin rather than shoot Mycroft – not knowing, or ignoring, that Mycroft would beg to be shot before he would stand by and accept Sherlock doing that to himself.

But then, as ever, despite all his power, he was useless when it came to saving his brother.

* * *

He should resent John Watson, for having the place Mycroft wanted. He can't. He can't because desperation makes him accept whatever necessity helps Sherlock the most.

Mycroft's love has never been necessary for Sherlock.

John Watson's love is.

Sherlock needs Mycroft to be his arch-enemy. So he will smile, and smile, and be what his brother needs.

And he can even stir himself to gratitude.

In their lives, Sherlock only ever comes at him once with true violence in his heart. From anyone else, Mycroft might have been prepared. But he doesn't see it coming. Hand twisted in the small of his back, chest pressed into the doorjamb at Baker Street, he can't stop the sudden upsurge of self-hatred in his belly.

But from now on he will never forget.

Sherlock is younger. But Sherlock is bigger, stronger – more comfortable with physicality than Mycroft will ever be. Sherlock was high, yes. But Sherlock has been high before. He may, God forbid, be high again. To show wariness would be to visibly concede power; nevermind that Sherlock has held all the power all along.

But if Mycroft flinches, Sherlock will _know_. And whatever ability the illusion of power might grant him to intercede in some way, will be lost forever.

So he won't.

John frees him. He goes home. He finds his room, and sits on the bed that used to belong to his parents. He stares at the crib – _no excuse for salvaging that, what was he thinking?_ – that he remembers from the inside. The sobs that come are entirely outside his control. He hasn't cried like that since Victor Trevor was killed, and Sherlock started to hide inside himself.

Sherlock considers John Watson family.

Mycroft only ever wanted Sherlock to live.

* * *

Mycroft despises legwork.

Of all his affectations, most fully deliberate, that one comes closest to being genuine. He hasn't the stomach for it. If Eurus is marked out by her complete disregard for the lives of others, Sherlock is the exact opposite – and Mycroft falls closer to Sherlock than Eurus; a fact for which he will always be grateful.

But a weak stomach is his permanent reminder of his failure. His own guise, returned to haunt him in a way he could never have predicted. He strove so hard for predictability, normality, that his rapid weight gain as a child marked him out in other, less pleasant ways.

Sherlock may have suspected, at one point, that he had fought his own body in a different way – but Sherlock was too immersed in drugs to look for the signs when it was going on. Mycroft tells himself that, rather than the more likely answer, which is that Sherlock saw the signs and didn't care. He's certainly deleted them by now regardless, but Mycroft takes care. Stress throws him back into bad places, and even his intelligence isn't enough for him to think his way out of loss of appetite and persistent nausea.

Ironically, there was nothing so recognizable as an eating disorder. It was simply…. Stress. The type only his family can instigate.

He could have his finger on the button to launch a missile that will start World War Three and not even register an increase in his heartrate.

Having to make a regular call to Sherrinford, however, caused his appetite to disappear faster than Sherlock after a case.

That doesn't change after his family knows about Eurus.

Predictably, it gets worse once the regular visits are instituted and his family requires his presence. He is forced to resort to meditation to engage in biofeedback, and taking an early night from work on the day before, to ensure his body is properly fueled for the day of the visit as he will be guaranteed unable to eat. The combination works well enough. The helicopter ride and its required ear protection gives him ample excuse not to engage with his family. It becomes time he hoards to collect himself.

That doesn't last; but then again, nothing ever does.

* * *

 _It worked_ , he has to keep reminding himself. Not perfectly. People died, and Eurus killed them. She never stopped. But Moriarty is dead. Sherlock is alive. So are Father and Mummy; so, for that fact, is Eurus – and possibly at a place of peace he could never give her. It wasn't the plan – the plan itself was less an articulable strategy than a goal. It couldn't be a plan; plans can be ruined with the loss of enough elements.

But it worked.

 _ **Fin**_


	2. The Scorpion and the Frog

THE SCORPION AND THE FROG

" _What goes around, comes around."_

In the end, it doesn't really matter that John Watson says the words, and not his brother.

 _So this is what it feels like_ , Mycroft thinks numbly. _Of course._ He's heard people say that some betrayals are worse than being stabbed in the heart. He'd always thought that particular descriptor demonstrated humanity's tendency towards the dramatic, conjuring that trite phrase. But this agonizing twist, all through him, that pulls and tears and throws his mind into chaos; it _doesn't stop_. A stiletto to the ventricles would at least be quick.

He wasn't even aware there was a sound recording until now, months after. All the officers had been wired, of course, but this was Sherlock and John and Lestrade in the shadowed ruins of Musgrave, far from where Eurus had been led away. He'd never been meant to know what was said, and wouldn't have, if not for Anthea.

His assistant. Grim-faced, set, with a "You need to know this, sir." Her stock phrase when she knew the contents were gruesome beyond imagining. Her way of warning him. _Need to know_.

He hasn't yet found a way to ask her how she discovered it.

But she was right.

He needed to know.

Needed to know that despite _everything_ , the fairest man Sherlock knows, the man who has been Sherlock's moral compass for years, thinks that Mycroft deserved Eurus consigning him to her cell.

In John's eyes – and thus, in Sherlock's, later if not sooner – Mycroft is no different from their raping murderess of a sister.

God, but he wishes he was even _surprised_ by it. The pain of the betrayal is not the common shock of _how-could-he_ , but the lesser known agony of _how-could-I?_

 _How could I let myself care?_

Caring is not an advantage. That does not actually make it a disadvantage. Not in many cases. Even caring set against the recipient's indifference is not necessarily a disadvantage, though it might be a drain on the giver. But caring offered and returned with hatred is worse than a mere disadvantage. It is a victim, baring vulnerable underbelly to a blood-stained predator. It is weakness laying itself out for no other purpose than to be exploited.

It is pain waiting to happen.

Did it never occur to _any_ of them that no one had automatically consigned a seven-year-old to a glass and concrete box with no human contact?

Mycroft hadn't known, but he hadn't _assumed_. He'd studied the files when the situation became his responsibility, and visited himself. The first facility had been not unlike a home. A gilded cage, certainly, but the gilding had mattered. Eurus had a room of her own, a bed, privacy, everything she asked for, and ample human interaction. Granted, it had been guards and physicians and psychologists, but after a time she'd been allowed to mingle with the other prisoners in that facility. That had been the first mistake. Luckily, only five people had died, over the course of two years and as many riots, eight fires, and countless manipulations.

The Sherrinford facility had still been under construction when Eurus reached puberty, and it became apparent that she needed more secure confinement. The third institution had not been shy about its status as a prison, or coy about its security measures. Nonetheless, in the space of the scant handful of years, Eurus had continued in the same vein, with a disturbing sexual element beginning to play into her actions as her body matured and she discovered new avenues of manipulation that correspondingly opened to her.

The first victims didn't even categorize themselves as such; instead, _they_ were the ones removed and imprisoned for abuse of a minor. Until Eurus got her hands on yet another fellow prisoner.

They found him in pieces. Eurus's willing participation in physical and psychological evaluation after the event was for her education, not theirs. To obtain a baseline for normal response to perceived sexual violation of another, one of her more astute psychiatrists had noted.

That one had requested reassignment soon after, and had been clever enough to seek counselling of her own. She was, thus far, the only person Mycroft could definitively name to have interacted with Eurus and come away relatively unscathed.

But it is more convenient for John to blame Mycroft; someone he knows can be hurt and feel pain. Blaming Eurus is reasonable but unfulfilling, akin to blaming a rattlesnake for its bite. _You wouldn't have gotten hurt if you'd just left it alone._

That reasoning ignores Eurus's own volition.

After being at her mercy, Mycroft wouldn't think that Eurus's deliberation would be an easy thing to forget. But he is apparently wrong. Even after being hauled up from the well in which Eurus had chained him, kept company by the bones of the little boy she'd put there when she was even younger than Victor Trevor had been, somehow _Mycroft_ is the villain.

He is shaking inside, though the hands clamped around the arms of his chair are perfectly steady. He wants to vomit, but his stomach is rock-solid.

That's the shape of her newest manipulation, at least on the surface. The victim. A role remarkably trite for her, in the vein of countless individuals perceived by society as smaller, weaker, or disadvantaged, and who learn to play off the stereotype straight into the system's politically-correct knee-jerk rejection of it. And it will work, because _none of them_ care to know her history, or the truth.

Because the truth is that Eurus had earned every security measure, every day without human contact, every year without sunshine or fresh air. She'd bought her imprisonment with other people's blood, shed both dispassionately and voraciously.

Mycroft has killed. He despises legwork for a reason. He can handle a gun, from the modern to the antique, and is skilled with a blade. But he can at least say that no one who died at his hands did so for any reason other than his self-defense. Despite what his brother thinks, he doesn't actually make people disappear.

Eurus killed because she wanted to. Life means nothing to her. The sanctity of an individual's body and mind were concepts that she acknowledged only as theories, waiting to be tested.

She wasn't taking any type of revenge on him, by locking him in her former cell, despite what Watson assumed. She was simply storing her next test subject for future use, in the place she thought him least likely to escape on his own. However long he might have languished there meant nothing to her.

His whereabouts clearly meant little to Sherlock or Watson, caught up as they were with Eurus's experiment at Musgrave.

It's a good thing that Mycroft learned early on to save himself, because no one was ever coming to his rescue. Even the inception of this case had been about Sherlock obtaining information, not about actually helping Mycroft. He'd never wanted to be saved; but he would have liked not to always be so utterly alone.

Sherlock had never been what anyone would call reliable. But Mycroft used to think – used to _hope_ – that in extremis, Sherlock might be counted on. It had never been a constant, but the variable had at least been present in his calculations.

He would have to remove that variable entirely going forward.

Especially in light of the visits, and the violins.

And now this.

He'd been spared Sherlock's automatic, vitriolic agreement, but the quiet contemplation in the wake of Watson's statement was worse. That was Sherlock, assessing the factors and coming to a decision. And utter silence on the topic, for months. Never a hint that Sherlock had known.

Now Mycroft really wished he could throw up.

" _What are you still doing here? Shouldn't you be off getting me a pardon or something, like a good big brother?"_

He'd spent his life shielding Sherlock from the consequences of his foolishness. Because Sherlock was extraordinary, his foolishness was so far beyond the normal that the consequences likely would have killed him in the majority of extrapolations Mycroft had run. So Mycroft had stepped in.

He hated that he wished now that he hadn't.

He'd had to. Of course he had to. He'd loved Sherlock, and Sherlock had been killing himself with drugs, his brilliant mind laying waste to his body and all around him.

Mycroft is the oldest. Mycroft has been corralling his siblings for their entire lives.

Mycroft is tired of being sacrificed for the sake of preserving two people who would, actively or out of carelessness, see him dead. Sherlock at least wouldn't vivisect him, but there's little more Mycroft feels he could say in his brother's favor.

 _"Go away, Mycroft."_

Eurus is Sherlock's new side project, and he is no more immune to her manipulations than he's ever been. Mummy and Father are barely accepting of the upper limit restriction on visits, constantly clamoring to spend time with the daughter who had been lost to them, and uncaring of Eurus's flat disregard for their presences. They do, however, approve of the duets.

He knows, deeper than reason, deeper than logic, deeper than the hollows of his bones, that nothing good will come of this. _But he doesn't know what._

He can't see what is to come, but that's only because the shape of it is obscured by tears.


	3. Serpent's Tooth

SERPENT'S TOOTH

In the time before Sherrinford, Mycroft had called his parents on average twice a month. He had made efforts to know their schedule, call when convenient, and never keep them on the phone for longer than they desired.

After Sherrinford, that stops.

He sees them during the visits to Eurus, visits that he cannot – dare not – escape; speaks with them during the calls arranging and confirming the details of transport, time, and location that make the visits possible. Nothing personal is discussed – they do not seek to know, and he lacks the courage to venture and be rebuffed.

He is not a child. He knows that anger does not mean that love is absent. This… is not anger. He is not afraid, precisely. But he has distance enough now to calmly evaluate all his own weak spots – the soft places in desperate need of armor.

 _Caring is not an advantage._

They are enraged with him; and the fury ebbs and flows across the days of the month in relation to the visits to Sherrinford.

His own anger avails him nothing.

They did not listen when he was twelve, thirteen, fifteen, forty-five – they will not listen now, and likely never again. Not about Eurus.

" _Alive?! For all these years? How is that even possible?!"_

" _What Uncle Rudy began ... I thought it best to continue."_

" _I'm not asking how you did it, idiot boy, I'm asking how could you?"_

" _I was trying to be kind."_

" _Kind?! You told us that our daughter was dead."_

" _Better that than tell you what she had become. I'm sorry."_

" _Whatever she became, whatever she is now, Mycroft ... she remains our daughter."_

" _And my sister."_

" _Then you should have done better."_

" _He did his best." Sherlock, surprisingly._

" _Then he's very limited."_

They have been silent on other topics, but he is not unintelligent enough to believe that silence to him means they have abandoned their foolish hopes of Eurus's release; a throwaway comment to Sherlock during one of the car rides back to London from the helicopter landing pad on the mainland makes that clear. He is briefly grateful for continuing the surveillance in his own vehicles.

It was why Uncle Rudi manufactured and maintained the ruse of Eurus's death in the first place. Four months without incident in the second facility, and they had begun to talk of bringing her home.

It is why Mycroft keeps an envelope, heavy with discs, marked by year and incident. It sits in the crib that once was his, in the one room of his home where few would find it – plain sight, and yet so very hidden. Precisely because no one cares enough to look.

He may not have the luxury of maintaining this last protection for very much longer.

For all their claims, his parents do not _know_.

He is convinced now that even if they are aware she tried to block their door the night Musgrave burned, that they have justified their way around the knowledge and rendered it irrelevant. They were informed, in the two years of her incarceration before Uncle Rudi faked her death, of "incidents" at the facilities. He has seen the recordings of those meetings, where the information was conveyed – using clean language. Brutality sanitized. Psychopathy softened. All to spare them.

It also cannot be denied that Eurus deduced soon after she was moved to the second facility that her parents were no longer a potential avenue of escape; therefore, she felt little need to hold herself back in her experiments.

Mycroft cannot even think her name without the corresponding index of incidents rising to the top of his mind.

When Uncle Rudi died, Mycroft became the last person alive who had seen all of the footage.

That works against him now, personally and professionally.

They cannot see Eurus without him. What kind feelings he has earned from his parents in the past eight months arise from that – with a corresponding level of resentment for what they see as his complicity in such being necessary in the first place. As long as he remains the unbending jailer, their anger will only grow. The gap between them will widen, into an unbreachable chasm. What Eurus's death could not destroy, her survival will decimate.

Better for him, by far, should the responsibility be removed from his hands entirely. Though Mummy at least has made it clear that even that is likely to be an unacceptable outcome – not when Mycroft ( _Idiot boy. Limited._ ) is accessible, perhaps predictable and controllable, to them.

He could never be used like that. Mycroft would rather the swift death of his relationship with his parents by his own hand, than a lingering, painful demise at Eurus's.

And she knows this, has doubtless accounted for it. Is waiting to test the mettle of whomever he deems worthy of receiving the keys to her captivity; because for all her knowledge and schemes, that is the one thing she does not know. Not yet.

However, the list of people he could trust with this burden are so few. Certainly not their parents. Sherlock is not to be considered. None of the other players on the board he has made a living manipulating are worth mention – nothing but equal cunning can even stand up against Eurus's manipulations, and repeat exposure only worsens the situation.

The fact remains that he must find someone.

… He cannot do this forever.

It's not a bitter pill to swallow; it's a relief.

Eurus is eight years younger, and without the stress that has poisoned Mycroft – who was already at a disadvantage to her in lifespan due to gender alone. If Sherrinford had gone differently; if Eurus had escaped, or Mycroft had died….

He had contingencies for one, but not the other. His own death is inevitable and likely to be premature. Eurus's escape hadn't been a factor.

He needs to sweep the chessboard clean and play out the possible moves without the pieces cluttering his way. All assumptions must be plucked from his consciousness. Nothing is certain, and nothing is safe.

But there will be a way.

Eyes closed, deep in the concrete box of his office, Mycroft settles into the tomblike silence and thinks. And sees the first glimmer of a plan.


End file.
